Nissan Motor Manufacturing in Europe is replacing some metal underhood components with high-performance polymers. It is using DuPont’s Minlon and Zytel products for the rocker cover and front cover of its 2.5-L turbodiesel engine. The move marks a first for Nissan Europe in metal replacement for underhood applications.
The parts were developed by the Spanish companies Fagor Ederlan (which has traditionally specialized in metal engine parts, transmission components, and car body manufacturing) and Maier, a manufacturer of plastic molded parts for automotive applications. Both companies are part of the MCC Mondragón Corporación Co-operativa. This strategic alliance provides multi-technological (plastic-metal) solutions responding to market demands, according to DuPont, which claims that Maier was able to achieve production cost savings of around 30% with a similar percentage reduction in component weight compared to aluminum equivalents.
The rocker cover is some 47.5 cm (18.7 in) long and 22.5 cm (8.9 in) wide and has a mass of about 1250 g (44 oz). It is molded from a mineral-filled and glass fiber-reinforced grade of Minlon nylon-66, meeting stiffness, strength, low warpage, and dimensional stability requirements that are essential for creating an enclosed seal to protect the valve control system and to prevent lubricating oil from escaping. The material can resist exposure to temperatures up to 150°C (302°F) and to hot oils and other chemicals.
The engine front cover is some 44 cm (17.3 in) long and 20 cm (7.9 in) wide (max), with a mass of 500 g (17.6 oz). It performs similar protective and sealant functions to the rocker cover. Because it has slightly smaller dimensions than the rocker cover, stability is less of an issue, according to DuPont, so a 30% glass fiber-reinforced grade of Zytel nylon resin was used.
The two companies worked together on the Nissan project to demonstrate that polymers can cut cost and weight for underhood applications. “By molding the two parts using high-performance polymers from DuPont, we were able to produce them to the same dimensions and levels of performance as the original cast-aluminum parts at a cost saving of 30-35% and weight saving of 40%,” said Mario Ordoñez, who is responsible for new materials at Maier. Fagor Ederlan’s role was provision of expertise relating to the product’s function via their experience in developing aluminum rocker covers.
DuPont assisted Maier with FEA of the molded parts, including simulations to improve gate locations, predict material behavior, and provide general processing recommendations. The project was spread over about 30 months, during which time Nissan developed, in parallel, metal counterparts that could be used in the event of the polymer components not meeting required testing or time requirements. The test work was carried out by IDIADA in Barcelona. In fact, the injection-molded parts met both criteria and are fitted to the engines of the Nissan Pathfinder and Navara.